Thermal Conductivity Detection Unit and Gas Chromatograph

The present invention relates to improving the accuracy of operation control of a heating device of a thermal conductivity detector.

Conventionally, as described in, for example, Japanese Unexamined Patent Application Publication No. 2020-041989 (Patent Literature 1), a thermal conductivity detector has been provided with a heating device (heater). This has minimized changes in the temperature of the portion that detects thermal conductivity, including the filament, due to factors other than the composition or concentration of the gas to be detected.

[Patent Literature 1] Japanese Unexamined Patent Application Publication No. 2020-041989

In conventional thermal conductivity detectors, from the viewpoint of reducing manufacturing costs, a general-purpose unit housed in a member with relatively high thermal conductivity has sometimes been adopted as the heating device. In such a case, the filament is housed in a member with relatively low thermal conductivity, along with a temperature sensor. In such a case, if the operation of the heating device is controlled using the temperature detected by the temperature sensor, the member housing the heating device may reach a target temperature before the detected temperature reaches the target temperature. As a result, when the detected temperature reaches the target temperature, the temperature of the member housing the heating device may exceed the target temperature. Therefore, if the heating device is controlled based on the detected temperature, a temperature overshoot may occur. This causes a situation where a long time is required for the temperature of the said portion in the thermal conductivity detector to stabilize during analysis using the thermal conductivity detector, and there has been a demand for improved accuracy in the operation control of the heating device in the thermal conductivity detector.

The present invention has been conceived in view of such circumstances, and an object thereof is to provide a technology for improving the accuracy of operation control of a heating device of a thermal conductivity detector.

A thermal conductivity detection unit according to an aspect of the present disclosure includes a thermal conductivity detector and a controller configured to control the thermal conductivity detector, wherein the thermal conductivity detector includes a first member, a second member having a higher thermal conductivity than the first member, a heating device housed in the second member, and a filament and a temperature sensor housed in the first member, and the controller is configured to control an output of the heating device with an output corresponding to a measurement result of the temperature sensor in a basic control, and when a temperature of the first member is outside a first range with respect to a temperature of the second member, control the output of the heating device with an output corresponding to the measurement result in an output reduction control, wherein in the output reduction control, the output of the heating device is controlled with an output that is reduced from the output corresponding to the measurement result in the basic control.

A gas chromatograph according to an aspect of the present disclosure includes a sample vaporization unit that generates a sample gas by vaporizing a sample, a column that separates components of the sample gas generated by the sample vaporization unit, and the above-described thermal conductivity detection unit, wherein the thermal conductivity detection unit detects the thermal conductivity of the sample gas for each component separated by the column.

According to an aspect of the present disclosure, a technology is provided for improving the accuracy of operation control of a heating device of a thermal conductivity detector.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and a description thereof will not be repeated.

1 FIG. 1 FIG. 1 10 20 30 40 50 60 70 80 is a block diagram showing a configuration of a gas chromatograph including an embodiment of a thermal conductivity detection unit. As shown in, a gas chromatographincludes a gas tank, a flow rate adjustment unit, a sample vaporization unit, a column, a flow rate adjustment unit, a switching valve, a thermal conductivity detector, and a control unit.

10 40 70 The gas tankstores a carrier gas for guiding a sample gas to the columnand the thermal conductivity detector. As the carrier gas, for example, an inert gas such as helium gas is used.

10 20 50 20 30 80 The gas tanksupplies the carrier gas to two flow rate adjustment unitsandvia a branch conduit. One flow rate adjustment unitsupplies the carrier gas at a predetermined flow rate to the sample vaporization unitbased on the control of the control unit.

30 30 30 40 20 30 The sample vaporization unitincludes an injector and a vaporization chamber. A sample is injected into the vaporization chamber of the sample vaporization unitvia the injector. The internal atmosphere of the vaporization chamber is maintained in a state where the sample vaporizes. Thereby, the sample injected into the vaporization chamber is vaporized therein. The sample vaporization unitsupplies the vaporized sample to the columnwhile mixing it with the carrier gas supplied from the flow rate adjustment unit. In the following description, the gas containing the components of the sample vaporized in the sample vaporization unitis collectively referred to as a sample gas.

40 40 30 40 76 70 The columnis housed in a column oven (not shown). In the column, each component of the sample gas supplied from the sample vaporization unitis separated. The columnsupplies the sample gas, separated for each component, to a sample introduction conduitof the thermal conductivity detector.

50 60 80 60 50 75 77 70 50 50 75 77 80 The flow rate adjustment unitsupplies a carrier gas at a predetermined flow rate to the switching valvebased on the control of the control unit. The switching valveis, for example, a three-way solenoid valve, and is connected to the flow rate adjustment unitand also to two later-described carrier gas introduction conduitsandof the thermal conductivity detector. The flow rate adjustment unitsupplies the carrier gas supplied from the flow rate adjustment unitto either one of the carrier gas introduction conduitsandbased on the control of the control unit.

50 75 77 60 50 75 77 50 75 77 70 Note that as a configuration for supplying the carrier gas passing through the flow rate adjustment unitto either one of the two carrier gas introduction conduitsand, a switching mechanism including a plurality of control valves and a branch conduit may be used instead of the switching valve. For example, a main conduit is connected to the flow rate adjustment unit, and two sub-conduits are respectively connected to the carrier gas introduction conduitsand. Also, two control valves are provided in the two sub-conduits, respectively. In this case, by controlling the open/closed state of the two control valves, the carrier gas supplied from the flow rate adjustment unitcan be selectively supplied to either one of the two carrier gas introduction conduitsandof the thermal conductivity detector.

70 71 72 73 74 75 77 76 78 70 71 74 70 70 70 70 70 70 The thermal conductivity detectoraccording to the present embodiment includes a first conduit, a second conduit, a third conduit, a fourth conduit, carrier gas introduction conduitsand, a sample introduction conduit, and an exhaust conduit, each extending linearly. These plurality of conduits are formed, for example, by metal piping. Among the plurality of conduits of the thermal conductivity detector, the first to fourth conduitstoare housed in a cell blockX together with a heating deviceH. The cell blockX is manufactured by processing and joining a plurality of metal plate-like members. In the cell blockX, the heating deviceH is housed in an aluminum blockA.

71 72 73 71 72 74 71 72 71 72 79 71 The first conduitand the second conduitare formed to face each other and extend in parallel. The third conduitis formed to connect one end of the first conduitand one end of the second conduit, and the fourth conduitis formed to connect the other end of the first conduitand the other end of the second conduit. A filament F is housed inside the first conduit. On the other hand, the filament F is not housed inside the second conduit. Note that a temperature sensoris further housed inside the first conduit.

73 73 73 73 73 73 73 71 73 73 a b c a c a c The third conduitis provided with a first gas introduction part, a second gas introduction part, and a third gas introduction part, arranged in this order. Among the first to third gas introduction partsto, the first gas introduction partis closest to the first conduit, and the third gas introduction partis closest to the third conduit.

75 73 70 76 73 70 77 73 70 a b c The carrier gas introduction conduitis formed to extend from the first gas introduction partto the outside of the cell blockX. The sample introduction conduitis formed to extend from the second gas introduction partto the outside of the cell blockX. The carrier gas introduction conduitis formed to extend from the third gas introduction partto the outside of the cell blockX.

74 74 78 74 70 74 74 78 78 78 70 a a a e The fourth conduitis provided with a gas outlet part. The exhaust conduitis formed to extend from the gas outlet partto the outside of the cell blockX. A through-hole is formed in the gas outlet part. Thereby, the internal space of the fourth conduitand the internal space of the exhaust conduitcommunicate with each other. The exhaust conduithas an exhaust portoutside the cell blockX.

70 80 70 30 40 70 The heating deviceH is controlled by the control unitand maintains the space inside the cell blockX at a temperature comparable to the temperature inside the vaporization chamber of the sample vaporization unitor the temperature inside the column oven housing the column. As the heating deviceH, for example, a cartridge heater is used.

80 1 80 The control unitis constituted by, for example, a CPU (Central Processing Unit) and a memory, or a microcomputer, and controls the operation of each component of the gas chromatographas described above. Further, the control unitof this example further includes a drive circuit for driving the filament F and a detection circuit for detecting a change in the resistance of the filament F.

60 75 77 The above-mentioned switching valveis switched between a first state of supplying the carrier gas to one carrier gas introduction conduitat a predetermined cycle (e.g., about 100 msec) and a second state of supplying the carrier gas to the other carrier gas introduction conduit.

73 70 60 73 73 76 72 73 73 71 a b a a In this case, inside the third conduitof the thermal conductivity detector, when the switching valveis in the first state, the pressure in the space on the side of the first gas introduction partbecomes higher than that of the second gas introduction part. Thereby, the sample gas supplied to the sample introduction conduitflows through the second conduittogether with a part of the carrier gas introduced from the first gas introduction part. The rest of the carrier gas introduced from the first gas introduction partflows through the first conduitas a reference gas.

73 70 60 73 73 76 71 73 73 72 c b c c On the other hand, inside the third conduitof the thermal conductivity detector, when the switching valveis in the second state, the pressure in the space on the side of the third gas introduction partbecomes higher than that of the second gas introduction part. Thereby, the sample gas supplied to the sample introduction conduitflows through the first conduittogether with a part of the carrier gas introduced from the third gas introduction part. The rest of the carrier gas introduced from the third gas introduction partflows through the second conduit.

80 Thereby, in the control unit, the thermal conductivity of the sample gas is measured based on the change in the resistance value of the filament F between when the reference gas passes around the filament F and when the sample gas passes around the filament F.

2 FIG. 2 FIG. 2 FIG. 1 FIG. 79 79 200 201 202 220 220 70 is a diagram showing an example of a control block related to the operation control of the heating device. The example inrepresents feedback (FB) control using the difference (error) between the measurement result of the temperature sensor(the temperature measured by the temperature sensor) and a target temperature.shows an FB control unit, a monitoring unit, an output limiting unit, and a controlled object. The controlled objectmeans the heating deviceH in.

200 220 220 220 Basically, the FB control unitcontrols the output of the controlled objectaccording to a basic control. In the basic control, the output (value) of the controlled objectis set based on the above-mentioned error, and the controlled objectis controlled to achieve the set output.

2 FIG. 201 79 71 70 In the example of, the monitoring unitdetermines whether the temperature of the member housing the filament F and the temperature sensor(the first conduit: the first member) is outside a first range with respect to the temperature of the member housing the heating device (the aluminum blockA: the second member), and also determines whether it is within a second range.

Whether the temperature of the first member is outside the first range with respect to the temperature of the second member, and whether the temperature of the first member is within the second range with respect to the temperature of the second member, may be determined based on the direct measurement results of both temperatures, or may be determined indirectly by other methods.

201 202 220 200 202 200 200 When the monitoring unitdetermines that the temperature of the first member is outside the first range with respect to the temperature of the second member, it instructs the output limiting unitto execute an output reduction control. The output reduction control is a control for reducing the output instructed to be realized by the controlled objectto be lower than the output set by the FB control unit. The output controlled by the output limiting unitmay be a value obtained by subtracting a constant value from the output set by the FB control unit, or may be “zero”, as long as it is lower than the output set by the FB control unit.

202 201 220 200 The output limiting unitexecutes the output reduction control in response to the instruction from the monitoring unit. Thereby, in the output reduction control, the output instructed to be realized by the controlled objectbecomes lower than the output set by the FB control unit.

201 202 220 220 200 Thereafter, when the monitoring unitdetermines that the temperature of the first member is within the second range with respect to the temperature of the second member, it instructs the output limiting unitto release the output reduction control. The control of the controlled objectreturns to the basic control. Thereby, the output instructed to the controlled objectreturns to the output set by the FB control unit.

79 220 220 In the present embodiment, an example of the “basic control” is PID (Proportional Integral Differential) control. The basic control, as long as it is a control that uses the measurement result of the temperature sensor, may be a control that switches on/off the output of the controlled objectaccording to the measurement result, or a control in which the output of the controlled objectis set as a linear function of the measurement result.

220 In the present embodiment, the controlled object(heating device) is housed in a member with a relatively high thermal conductivity. This allows the heat from the heating device to be efficiently propagated to other elements in the thermal conductivity detector. In this specification, aluminum (aluminum block) is shown as an example of a member with a relatively high thermal conductivity, but it is not limited to this, and other types of members such as copper may be used.

Further, the filament is housed in a member with a relatively low thermal conductivity. This makes it possible to stabilize the temperature of the filament and its surroundings. In this specification, stainless steel is shown as an example of a member with a relatively low thermal conductivity, but it is not limited to this, and other types of members such as titanium may be used.

Furthermore, the temperature sensor is housed in the same member as the filament, and the operation control of the heating device is performed based on the measurement result of the temperature sensor and in accordance with the basic control. This allows the temperature around the filament to be more reliably reflected in the measurement result of the temperature sensor and, in turn, more reliably reflected in the operation control of the heating device.

Then, in the operation control of the heating device, when the temperature of the heating device rises and the temperature of the member housing the heating device (the second member) deviates significantly from the temperature of the member housing the filament and the temperature sensor (the first member) (when the temperature difference between them is outside the first range), the output of the heating device is temporarily adjusted to be lower than the output corresponding to the measurement result in the basic control. This suppresses the occurrence of overshoot.

Thereafter, when the temperature of the member housing the filament and the temperature sensor (the first member) approaches the temperature of the member housing the heating device (the second member) (when the temperature difference between them is within the second range), the control of the output of the heating device is returned to the above-mentioned basic control. This allows the heating device to be controlled so that the temperature of the filament reaches the target temperature earlier.

As described above, according to the present disclosure, the operation of the heating device is controlled to make the temperature of the filament reach the target temperature earlier while suppressing the occurrence of overshoot.

71 70 In the present embodiment, whether the temperature of the first member (the first conduit) is outside a first range with respect to the temperature of the second member (the aluminum blockA) and whether the temperature of the first member is within a second range with respect to the temperature of the second member are determined using a threshold value.

3 FIG. 3 FIG. 10 20 1 70 is a diagram showing an example of information used for setting a threshold value.shows a graph Gand a graph Gobtained in a gas chromatographmodified for threshold setting. The modification is the addition of a temperature sensor (hereinafter also referred to as an “additional sensor”) attached to the aluminum blockA.

10 70 79 70 79 70 10 70 11 79 12 13 70 11 12 13 Graph Gshows the result of on/off control of the heating deviceH using the temperature sensorand a target temperature (e.g., 80° C.) (controlling the output of the heating deviceH to 100% if the measurement result of the temperature sensoris equal to or lower than the target temperature, and turning off the heating deviceH (output to 0%) if the measurement result exceeds the target temperature). In graph G, changes in the output (%) of the heating deviceH (line L), the measurement result (° C.) of the temperature sensor(line L), and the rate of the measurement result (° C./sec) (line L) with the elapsed time from the start of heating by the heating deviceH are shown. The vertical axis for lines Land Lis shown on the right side. The vertical axis for line Lis shown on the left side.

20 70 70 70 20 70 21 79 22 23 70 21 22 23 Graph Gshows the result of on/off control of the heating deviceH using the above-mentioned additional sensor and the target temperature (controlling the output of the heating deviceH to 100% if the temperature measured by the additional sensor is equal to or lower than the target temperature, and turning off the heating deviceH (output to 0%) if the measurement result exceeds the target temperature). In graph G, changes in the output (%) of the heating deviceH (line L), the measurement result (° C.) of the temperature sensor(line L), and the rate of the measurement result (° C./sec) (line L) with the elapsed time from the start of heating by the heating deviceH are shown. The vertical axis for lines Land Lis shown on the right side. The vertical axis for line Lis shown on the left side.

10 11 70 In graph G, line Lindicates that after the output of the heating deviceH was turned on at 100%, the output was switched off at 14 seconds. Thus, the rise time from the start of heating in the first member is 14 seconds.

10 11 79 70 Further, in graph G, line L, as indicated by the dashed line, shows that the measurement result of the temperature sensorincreases by 15° C. after the output of the heating deviceH is switched off.

4 FIG. 3 FIG. 3 FIG. 4 FIG. 13 10 20 is a diagram showing the information shown inwith different annotations from. In, the dashed line indicates the timing at which the rate of the measurement result in line Lof graph Greaches the maximum value (maximum heating rate (0.3° C./sec)). The dashed line further indicates the same elapsed time in graph Gas the said timing.

79 12 22 79 At the said timing, the measurement result of the temperature sensoris about 60° C. as shown by line L, and the temperature measured by the additional sensor is about 75° C. as shown by line L. This means that when the maximum heating rate appears in the measurement result of the temperature sensor, there is a temperature difference of 15° C. or more between the first member and the second member.

5 FIG. 3 FIG. 3 FIG. 5 FIG. 13 10 20 is a diagram showing the information shown inwith different annotations from. In, the dashed line indicates the timing at which the heating rate reaches 0.1° C./sec in line Lof graph G. The dashed line further indicates the same elapsed time in graph Gas the said timing.

0.1° C./sec is an example of a heating rate set based on the maximum heating rate. More specifically, if the heating rate exceeds the maximum heating rate, the temperature difference between the first member and the second member cannot be determined. Therefore, the temperature between the first member and the second member can be specified based on the timing when the heating rate reaches a given value lower than the maximum heating rate. As the heating rate to be used, for example, a value of about ⅓ of the maximum heating rate is used.

5 FIG. 79 12 22 79 At the timing shown in, the measurement result of the temperature sensoris about 46° C. as shown by line L, and the temperature measured by the additional sensor is about 51° C. as shown by line L. This means that when the heating rate in the measurement result of the temperature sensoris 0.1° C./sec, the temperature difference between the first member and the second member is about 5° C.

3 FIG. 3 FIG. 70 79 As explained with reference to, the time required from the start of heating to the rise in the first member (rise time) is 14 seconds. This means that a delay of 14 seconds occurs until the first member reaches the target temperature from the start of heating. Also, as explained with reference to, after the output of the heating deviceH is switched off, the measurement result of the temperature sensorincreases by 15° C.

4 FIG. 79 Further, as explained with reference to, the maximum value (maximum heating rate) in the measurement result of the temperature sensoris 0.3° C./sec, and there is a temperature difference of 15° C. or more between the first member and the second member when the maximum heating rate appears.

5 FIG. Furthermore, as explained with reference to, when the heating rate is 0.1° C./sec, the temperature difference between the first member and the second member is about 5° C.

79 70 From the above, when the heating rate is 0.1° C./sec, even if the above-mentioned delay (14 seconds) occurs, the temperature increase is suppressed to a maximum of 1.4° C. This temperature is smaller than the temperature difference (about 5° C.) between the first member and the second member when the heating rate is 0.1° C./sec. Therefore, by changing the control from the basic control to the output reduction control on the condition that the heating rate in the measurement result of the temperature sensoris 0.1° C./sec or more, overshoot in the first member can be avoided. In other words, the heating rate being 0.1° C./sec or more is an example of a disengagement condition (a condition for disengaging the control of the heating deviceH from the basic control and transitioning to the output reduction control) being met. In this sense, “0.1° C./sec” can be an example of a threshold (start threshold) for switching the control from the basic control to the output reduction control.

79 79 1 The fact that the heating rate in the measurement result of the temperature sensoris 0.1° C./sec or more constitutes an example of the temperature of the first member being outside a controllable range with respect to the temperature of the second member (i.e., outside the first range). More specifically, after reaching the maximum heating rate (0.3° C./sec), the heating rate hardly increases, but the difference between the first temperature and the second temperature tends to widen. Unless the heating rate is equal to or less than the maximum heating rate, it cannot be said that the temperature difference is within a controllable range. In this sense, it should be determined that the temperature of the first member is outside the controllable range with respect to the temperature of the second member on the condition that the heating rate in the measurement result of the temperature sensorexceeds the maximum heating rate. In the present embodiment, in consideration of individual differences among the components of the gas chromatograph, 0.1° C., which is slightly smaller than 0.3° C., is adopted as the threshold in order to reliably specify that the temperature difference is within the controllable range.

1 Note that when the above-mentioned additional sensor is provided in the gas chromatograph, as another example of the start threshold, the difference between the direct measurement results of the respective temperatures of the first member and the second member may be adopted. More specifically, the control may be switched from the basic control to the output reduction control on the condition that this temperature difference is equal to or greater than a given value (for example, about 5° C.) . In this case, the temperature difference being equal to or greater than the said given value is another example of the disengagement condition being met.

79 79 70 70 70 When the heating rate in the measurement result of the temperature sensoris less than 0.1° C./sec, the control is changed from the output reduction control to the basic control. The fact that the heating rate in the measurement result of the temperature sensoris less than 0.1° C./sec is an example of a return condition (a condition for returning the control of the heating deviceH from the output reduction control to the basic control). By returning the control of the heating deviceH to the basic control in response to the satisfaction of the return condition, the output of the heating deviceH can be controlled to stabilize the temperature of the first member near the target temperature earlier in a state where the possibility of overshoot occurring in the first member is low.

79 The fact that the heating rate in the measurement result of the temperature sensoris less than 0.1° C./sec constitutes an example of the temperature of the first member being within the second range with respect to the temperature of the second member. In this case, “0.1° C./sec” constitutes an example of a threshold (release threshold) for switching the control from the output reduction control to the basic control.

The release threshold may be the same value as the above-mentioned start threshold. In this case, the second range means the same range as the first range.

79 Note that the release threshold may have a slightly larger value than the start threshold. More specifically, a value larger than the start threshold by about 0.5° C. may be set as the release threshold so that chattering does not occur even if the actual measured value of the temperature sensorfluctuates instantaneously due to disturbance and/or noise. For example, if the start threshold is 0.10° C./sec, the release threshold may be 0.15° C./sec.

1 Note that when the above-mentioned additional sensor is provided in the gas chromatograph, as another example of the release threshold, the difference between the direct measurement results of the respective temperatures of the first member and the second member may be adopted. More specifically, the control may be switched from the output reduction control to the basic control on the condition that this temperature difference is less than a given value (for example, about 5° C.). In other words, this temperature difference being less than the given value is another example of the return condition being met.

6 FIG. 6 FIG. 6 FIG. 6 FIG. 70 71 80 80 80 71 is a flowchart of an output control process of the heating deviceH for controlling the first conduithousing the filament F to a target temperature. In one implementation, the process ofis executed by the CPU of the control unitexecuting a given program. In other words, an example of the “controller” in the present embodiment is realized by the control unitexecuting the said given program. In one implementation, the control unitstarts the process ofin response to being instructed to start the temperature control of the first conduit. The content of the process will be described below with reference to.

10 80 70 10 200 2 FIG. In step S, the control unitstarts the basic control for the heating deviceH. The control in step Scorresponds to the function as the FB control unit().

20 80 80 20 20 20 30 20 201 2 FIG. In step S, the control unitdetermines whether the above-mentioned “disengagement condition” has been met. The control unitrepeats the control of step Suntil it determines that the “disengagement condition” has been met (NO in step S), and when it determines that the “disengagement condition” has been met (YES in step S), it proceeds to step S. The control in step Scorresponds to the function as the monitoring unit().

30 80 70 30 202 2 FIG. In step S, the control unitswitches the control for the heating deviceH from the basic control to the output reduction control. The control in step Scorresponds to the function as the output limiting unit().

40 80 80 40 40 40 10 70 40 201 2 FIG. In step S, the control unitdetermines whether the above-mentioned “return condition” has been met. The control unitrepeats the control of step Suntil it determines that the “return condition” has been met (NO in step S), and when it determines that the “return condition” has been met (YES in step S), it returns the control to step S. Thereby, the control for the heating deviceH is returned to the basic control. The control in step Scorresponds to the function as the monitoring unit().

6 FIG. 80 70 10 80 70 10 When starting the process of, the control unitmay execute a control to set the output of the heating deviceH to 100% before the basic control of step S. In one implementation, the control unitmay execute a control to set the output of the heating deviceH to 100% instead of PID control during a period when the temperature difference between the first member and the second member is considered to be 20° C. or more, and when it determines that such a period has ended, it may execute the heating control of step S.

70 70 79 79 When the temperature difference between the first member and the second member is 20° C. or more, the proportional term in the PID control becomes 100% or more. The range where the proportional term is 100% or less is called the “proportional band”. Outside the “proportional band”, the output of the heating deviceH is controlled to 100% in order to rapidly raise the temperature of the second member. It is considered that the possibility of overshoot is low even if the basic control of the output of the heating deviceH is performed when the difference between the measurement result of the temperature sensorand the temperature measured by the additional sensor becomes 15° C. or more (that is, when the measurement result of the temperature sensoris 15° C. or more below the target temperature). The “20° C.” is adopted as an example of a value equal to or greater than the said difference.

In this specification, the control of the heating device of a thermal conductivity detector has been described with an example where the thermal conductivity detector is mounted on a gas chromatograph. However, the control of the heating device of the thermal conductivity detector described in this specification is not limited to the case where the thermal conductivity detector is mounted on a gas chromatograph, and can be applied to the control of the heating device of a thermal conductivity detector in any case.

(Item 1) A thermal conductivity detection unit according to one aspect may include a thermal conductivity detector and a controller configured to control the thermal conductivity detector, wherein the thermal conductivity detector includes a first member, a second member having a higher thermal conductivity than the first member, a heating device housed in the second member, and a filament and a temperature sensor housed in the first member, and the controller is configured to control an output of the heating device with an output corresponding to a measurement result of the temperature sensor in a basic control, and when a temperature of the first member is outside a first range with respect to a temperature of the second member, control the output of the heating device with an output corresponding to the measurement result in an output reduction control, and in the output reduction control, the output of the heating device is controlled with an output that is reduced from the output corresponding to the measurement result in the basic control. It is understood by those skilled in the art that the plurality of exemplary embodiments described above are specific examples of the following aspects.

1 (Item 2) In the thermal conductivity detection unit described in Item 1, the controller may determine that the temperature of the first member is outside the first range with respect to the temperature of the second member when a temperature increase value per unit time in the measurement result is equal to or greater than a predetermined heating rate. According to the thermal conductivity detection unit described in Item, a technology is provided for improving the accuracy of operation control of a heating device of a thermal conductivity detector.

(Item 3) In the thermal conductivity detection unit described in Item 1 or 2, the controller may be configured to, after the output reduction control, control the output of the heating device with the output corresponding to the measurement result in the basic control when the temperature of the first member is within a second range with respect to the temperature of the second member. According to the thermal conductivity detection unit described in Item 2, a temperature sensor for measuring the temperature of the second member is not required, and the manufacturing cost of the thermal conductivity detection unit can be reduced.

(Item 4) In the thermal conductivity detection unit described in Item 3, the controller may determine that the temperature of the first member is within the second range with respect to the temperature of the second member when a difference between the measurement result and a target temperature in the control of the output of the heating device is equal to or less than a predetermined temperature. According to the thermal conductivity detection unit described in Item 3, the operation of the heating device is controlled to make the temperature of the filament reach a target temperature earlier while suppressing the occurrence of overshoot.

(Item 5) In the thermal conductivity detection unit described in any one of Items 1 to 4, the basic control may be PID control. According to the thermal conductivity detection unit described in Item 4, a temperature sensor for measuring the temperature of the second member is not required, and the manufacturing cost of the thermal conductivity detection unit can be reduced.

(Item 6) In the thermal conductivity detection unit described in any one of Items 1 to 5, the output reduction control may include turning off the output of the heating device. According to the thermal conductivity detection unit described in Item 5, the operation of the heating device can be controlled with high accuracy with respect to the target temperature.

(Item 7) In the thermal conductivity detection unit described in any one of Items 1 to 6, the output reduction control may include calculating a value obtained by subtracting a constant value from the output corresponding to the measurement result in the basic control as the output of the heating device. According to the thermal conductivity detection unit described in Item 6, overshoot in the first member can be more reliably avoided.

(Item 8) In the thermal conductivity detection unit described in any one of Items 1 to 7, the first member may include stainless steel, and the second member may include aluminum. According to the thermal conductivity detection unit described in Item 7, overshoot in the first member is avoided, and the temperature of the first member can be stabilized near the target temperature early.

(Item 9) A gas chromatograph according to one aspect may include a sample vaporization unit that generates a sample gas by vaporizing a sample, a column that separates components of the sample gas generated by the sample vaporization unit, and the thermal conductivity detection unit described in any one of Items 1 to 8, wherein the thermal conductivity detection unit detects the thermal conductivity of the sample gas for each component separated by the column. According to the thermal conductivity detection unit described in Item 8, heat from the heating device is easily propagated to other elements, and the temperature near the filament is stabilized.

According to the gas chromatograph described in Item 9, a technology is provided for improving the accuracy of operation control of a heating device of a thermal conductivity detector.

The embodiments disclosed this time should be considered as illustrative in all respects and not restrictive. The scope of the present disclosure is indicated by the claims rather than by the description of the embodiments above, and all changes that come within the meaning and range of equivalency of the claims are intended to be embraced therein. Further, it is intended that each technology in the embodiments can be implemented alone or in combination with other technologies in the embodiments as much as possible, as necessary.

1 10 20 50 30 40 60 70 70 70 70 71 75 77 76 78 78 79 80 200 201 202 220 10 20 11 12 13 21 22 23 e Gas chromatograph,Gas tank,,Flow rate adjustment unit,Sample vaporization unit,Column,Switching valve,Thermal conductivity detector,A Aluminum block,H Heating device,X Cell block,First conduit,,Carrier gas introduction conduit,Sample introduction conduit,Exhaust conduit,Exhaust port,Temperature sensor,Control unit,FB control unit,Monitoring unit,Output limiting unit,Controlled object, F Filament, G, GGraph, L, L, L, L, L, LLine.